This invention relates to the gasification of slurries of ash-containing solid carbonaceous fuel. More specifically, it relates to the catalytic gasification of the particulate carbon and the carbon in the unconverted portion of ash-containing solid carbonaceous fuel entrained in the raw effluent synthesis gas stream leaving a refractory lined free-flow gas generator for the noncatalytic partial oxidation of slurries of ash-containing solid carbonaceous fuel, such as slurries of coal dispersed in a liquid medium i.e., water, liquid hydrocarbonaceous fuel, and mixtures thereof.
As supplies of petroleum gradually diminish, coal which is America's most abundant form of fossil fuel will play an increasingly major role in providing for the nation's energy requirements. One ton of coal contains the same amount of energy as three to four barrels of crude oil. Accordingly, in the future it will become necessary to produce an increasing fraction of liquid and gaseous fuels from coal. The gas produced by this invention may be used with or without further processing and/or purification as a gaseous fuel or as feedstock for the catalytic synthesis of liquid fuels.
Synthesis gas, fuel gas, and reducing gas may be produced from coal by well known gasification processes. For example, coassigned U.S. Pat. Nos. 3,544,291 and 4,289,502 respectively relate to a process for the partial oxidation of slurries of coal, and to an apparatus for producing cleaned and cooled synthesis gas by the partial oxidation of solid carbonaceous fuel. No catalysts or slurries of solid carbonaceous fuels are used in the processes described in U.S. Pat. Nos. 3,988,123 and 4,060,397. U.S. Pat. No. 4,094,650 pertains to a process for producing a CH.sub.4 -containing gas in a fluidized bed of catalyst comprising a carbon-alkali metal reaction product. The catalytic material is transported into an uncooled reaction vessel where it is maintained in a fluidized bed by means of an upflowing mixture of steam and a portion of recycle product gas.
The normal residence time in a conventional free-flow refractory lined partial oxidation gas generator is in the range of about 1-5 seconds. With short dwell times a small amount of the solid fuel particles may pass unreacted through the reaction zone of the gas generator. Such short dwell times may be insufficient to allow the envelope of liquid carrier surrounding each solid fuel particle to vaporize, and for the gases to then contact and react with the carbon in the solid fuel particle. When this occurs, the combustion efficiency of the process is reduced; and, the cost of cleaning the raw synthesis gas to remove the unconverted particles of solid fuel is increased. This problem is reduced or eliminated by the subject process in which substantially all of the carbon in the ash-containing solid carbonaceous fuel may be converted into carbon oxides.